Arc-lamp-feeding mechanism



Sept. 29, 1925.

E. THOMSON Anc LAMP FEEDING MEGHANISM Filed July 25, 1923 fm/enof; //hUThomson,

Patented Sept. 29, 192.5.

UNITED' STATES 1,555,775 PATENT orifice.

ELIHU THOISON, I Lm, IABSACRUSETTS, ASSIGNOB. T0 GENERAL ELECTRIC COM-Pm, A. CORPORATION OF NEW YORK.

ABC-LAMP-FEEDING HECHANIBM.

Application led July 25, 1923. Serial No. 653,801.

To all whom. 'it my concern.'

Be it known that I, ELIHU THOMSON, a citizen of the United States,residing at Lynn, in the county of Essex, State of Masu sachusetts, haveinvented certain new and useful Improvements in Arc-Lamp-FeedingMechanisms of which the following is a specification.

My invention relates to feeding mechanisms for are lamps. Moreparticularly it relates to feeding mechanisms of the type which areoperated by an electric motor through the medium of suitable gears.Heretofore are lampshave been made with a' constant feed arr ementwhichis operated by gearing up the electrode holders and an electric motorthrough the medium of suitable mechanism. This gearing mechanism is sodesigned as to feed the electrodes toward or away from each other at apredetermined rate, determined by the rate of consumption of a standardelectrode. However, electrodes do not all run the same.

Electrodes from one batch may be consumed' faster orslower than those ofa' different batch. The result is. that if the mechanism is designed andset to feed at a certain rate, although such rate ma be satisfactory forone set of electrodes, 1t will be either too slow or too fast for adifferent set with the result that the arc is thrown out of adjustmentand thrown out of focus if, for example, the device is used inconnection with a searchlight or motion picture machine. It is obvious,however, that by varying the rate of rotation of the motor the rate offeed may be variedaccordingly.

It is an object of my invention to provide means for varying the rate ofrotation of the motor to the extent desired by providing a dam ingdevice through the medium of which the load of the armature of the motoris varied and make it possible to use in the arc 'lamp electrodes whichare not uniform. It is also an object of my invention to provide otherdetails of improvement tending to increase the eliciency andserviceability of an arc lam of the above character.

To accomplish the 'foregoing and other useful ends my inventioncomprises means hereinafter more fully set forth, and claimed, referencebeing h'ad to the accompanying drawing.

' In Fig. 1 I show the device in elevation and partly in section; Fig. 2is a top view of the same device; Fig. 3 shows one form of the dampingelement of the lamp; Fig. t another form of the damping element, andFie" 5 is a diagrammatic lay-out of the 'rieal circuits of theapparatus. it ring more in detail to the accompartying drawingselectrodes 1 and 2 are moved by the threads 3 and 4i respectively on thescrew 5, which latter is in frictional engagement with the gear wheel 6.gear wheel 6 is in engagement with the 'worm 7, the shaft 8 of whichworm is sunu ported by the bearings 9 and 10. To the shaft '8 there issecured another gear wheel 11 which latter is driven by the motor 12through the medium of the worm 13 on the motor shaft. It will beobserved that the lower portion of the screw 5 extends through thebearing 14 and is provided at its lower end with a head 15 which isrigidly secured to the screw 5 so that by turning the head the screw maybe turned. In view of the frictional engagement between the screw o andthe gear 6, as previously stated, the screwmay be rotated irrespectiveof the gear 6 by turning the knob 15. This arrangement is ahandadjustment superimposed upon the motor feed for use in case ofemergency. The engagement between the screw 5 and the. gear wheel 6 isvin the nature of a friction clutch. It will be observed that the shaftis tapered and the bore in the hub 6 of the gear 6 is correspondinglytapered. The gear is kept in working engagement with the screw 5 bymeans of the spring 16 which is interposed between bearing 14 andthe'hub 6a of the gear. The force of the spring tends normally to forcethe gear up and maintain it forced on the screw 5 with suliicientpressure to transmit the driving force necessary for operating the screw5 .by the motor 12. This eneral arrangement for drivin electrodes ymotor thus far described in connection with the detailed description ofFig. 1 is more or less old in the art and alone does not constitute myinvention. l

I will now describe the damping arrangement through the medium of whichthe rate of feed may be varied to suit electrodes of different kinds. Onthe motor shaft 17 I provide a metal disk 18 rigid with the shaft.

n net 19. This magnet may be madein the form of a horse shoe and thedisk may be The proximity to thisdisk, I provide a magarranged to rotatebetween the poles as clearly indicated in the drawing. A s shown in Fig.3, the magnet is pivoted so that it may be rotated about the axis 20. Bmoving the magnet 19 with respect to t e axis of the disk, thedampingaction of the magnetic flux, on a disk, ma be varied. For the purpose ofvarying t e relation of the magnet to the disk an adusting screw 21 maybe provided. The ampin ma et may be an electromagnet as in icate in Fig.3, or it may be a permanent magnet, such as magnet 22, as indicated inFig. 4. Furthermore, there may be a number of magnets acting` upon thedisk instead of only one. It will be observed that in Fig. 4 thepermanent'electromagnet is pivoted in an upright position and may beadjusted through the medium of the set screw 23. Furthermore, thedamping structure may be a cylinder in place ofthe disk or a squirrelcage rotor in a suitable magnetic field which is ad'ustable with respectto the rotor as is well nown in the field of induction motors.

Referring to Fig. 5 a suitable source of current such as a dynamo 25 isshown across the conductors 26 and 27. Across said conductors is placedthe arc, the electrodes 3 and 4 of which are shown. In series with thearc there .is provided a stabilizing resistance 28. Across thestabilizing resistance is the winding 29 of the electromagnet 19, Fig.3. Across the source of current is connected the motor 12, the field 30of which is shown in shunt with the armature. In series with the motorthere is connected a resistance 31 in order to make the motor moresensitive in changes in load. With the arrangement shown the greater thecurrent drawn through the arc the greater will be the energizationof theelectromagnet 19 and consequently the greater will be the load on themotor. Therefore with the circuit and arrangement indicated by Fig. 5the s stem becomes substantially automatic a ter the first adjustmentfor if the current rises in the are, due to the carbons approaching oneanother, the damping action of the damping electromagnet becomes`greater as it becomes more and more energized due to the rise incurrent throu h the arc. motor slows up giving the carbons more time toburn and thereby increase the length of the arc. When, however, thereverse is the case, as when the current in the arc has been reduced,due to too great a lengthening of the are, then the damping ma et isautomatically weakened and the spee of thel electrode automaticallyaccelerated. A condition of equilibrium therefore exists between thesetwo conditions which will be maintained so that the arc will burnsteadily with the electrodes at the proper working distance from eachother.

' What I claim as new and desire to secure by Letters Patent of theUnited States, is:

1. In an arc lamp -an electrode feedingmechanism and an electric motorfor operat- Y ing said mechanism to continuously feed one of theelectrodes, a magnet, an'd a metallic disk connected with the motor tobe rotated thereby, said disk interposed in the ma etie circuit of saidmagnet, said disk an magnet serving as a magnetic brake for the motor,and means for varying the strength of the magnetic field of the ma etabout said disk for varying the rate of ed of said electrode. r

2. In combinationy with a source of current, an are lamp, an electrodefeeding mechanism, an electric motor for driving said mechanism and anelectro ma et damper device for varying the speed o the motor andvarying the rate of motion of the feeding mechanism, and resistance inseries with said motor to increase the sensitiveness o f the motor tovariations in load, and a resistance in series with the.' arc tostabilize the arc and a shunt circuit about said arc-stabilizingresistance, said shunt circuit for energizing said electromagnet dampindevice.

In wltness whereof, I have hereunto set my hand this twenty-third da ofJul 1923.

. ELIHU HOM ON.

The result is, therefore, that t e i

